Revisiting nonlocal electron-energy transport in inertial-fusion conditions

Correct modeling of the electron-energy transport is essential for inertial confinement fusion target design. Various transport models have been proposed in order to extend the validity of a hydrodynamical description into weakly collisional regimes, taking into account the nonlocality of the electron transport combined with the effects of self-generated magnetic fields. We have carried out new experiments designed to be highly sensitive to the modeling of the heat flow on the Ligne d'Intégration Laser facility, the prototype of the Laser Megajoule. We show that two-dimensional hydrodynamic simulations correctly reproduce the experimental results only if they include both the nonlocal transport and magnetic fields.

Clinical and pharmacological risk factors for acute graft-versus-host disease after paediatric bone marrow transplantation from matched-sibling or unrelated donors

The aim of this study was to identify the risk factors for acute graft-versus-host disease (aGVHD) in children transplanted from a matched-sibling donor (MSD) or an unrelated donor (UD). In all, 87 children consecutively underwent allogeneic bone marrow transplantation (BMT) from MSD (n=36), and UD (n=51). GVHD prophylaxis included CsA alone (n=33) or with MTX (n=51). ATG was added in UD-BMT and thalassemic recipients. CsA whole-blood concentrations were measured by EMIT and the dosing regimen was monitored by Bayesian pharmacokinetic modelling. Trough blood concentration (TBC) during the first 2 weeks post transplantation was lower in children who developed grade II-IV aGVHD than those developing no GVHD or only grade I (57+/-9 vs 94+/-8 ng/ml, P=0.007), whereas peak blood concentration and area under concentration curve vs time were similar in both groups. TBC <85 ng/ml and 'use of MTX' were associated with aGVHD in MSD-SCT (P=0.003 and 0.007, respectively) as well as in UD-SCT (P=0.006 and 0.003). Donor age >or=8 years was significant only in MSD-BMT. Our results have shown the significant decisive role of pharmacological factors such as CSA TBC or use of MTX in the occurrence of GVHD in MSD as well as in UD paediatric BMT.

Relationship between CsA trough blood concentration and severity of acute graft-versus-host disease after paediatric stem cell transplantation from matched-sibling or unrelated donors

In order to determine optimal CsA trough blood concentrations (TBC) in the early post transplantation period, we analysed relationships between TBC and acute graft-versus-host disease (aGVHD) in paediatric SCT. A total of 94 children consecutively underwent allogeneic stem cell transplantation (SCT) from: matched-sibling (MSD) (n=36), mismatched-related (MMRD) (n=3) and unrelated donors (UD) (n=55). GVHD prophylaxis usually included CsA alone or with methotrexate. Antithymocyte globulin was added in UD-SCT. TBC during the first weeks of post transplantation were estimated retrospectively by a Bayesian pharmacokinetic method and statistically associated with aGVHD. In MSD-SCT, the mean TBC during the first 2 weeks post transplantation were 42+/-10 and 90+/-7 ng/ml, respectively, in patients with grade II-IV and 0-I aGVHD (P=0.001). In SCT from UD and MMRD, TBC were 73+/-4 vs 95+/-8 ng/ml (P=0.284). For TBC >85 ng/ml, no patient developed grade II-IV aGVHD, 10 developed mild aGVHD and 30 had no aGVHD. For TBC <65 ng/ml, 7/11 patients receiving an MSD-SCT and 4/18 receiving an UD- or MMRD-SCT developed grade II-IV aGVHD. The mean TBC corresponding to each grade were: no GVHD: 101+/-10 ng/ml, mild: 77+/-11 ng/ml, moderate: 61+/-13 ng/ml, severe: 56+/-15 ng/ml (P <0.001). These results reveal a strong relationship between TBC during the early post transplantation period and the severity of aGVHD in paediatric SCT.

Comparisons between antimicrobial pharmacodynamic indices and bacterial killing as described by using the Zhi model

Various suggestions have been made for empirical pharmacodynamic indices of antibiotic effectiveness, such as areas under the drug concentration-time curve in serum (AUC), AUC > MIC, AUC/MIC, area under the inhibitory curve (AUIC), AUC above MIC, and time above MIC (T > MIC). In addition, bacterial growth and killing models, such as the Zhi model, have been developed. The goal of the present study was to compare the empirical behavior of the Zhi model of bacterial growth and killing with the other empirical pharmacodynamic indices described above by using simulated clinical data analyzed with the USC*PACK PC clinical programs for adaptive control of drug therapy, with one model describing a concentration-dependent antibiotic (tobramycin) and another describing a concentration-independent antibiotic (ticarcillin). The computed relative number of CFU was plotted against each pharmacodynamic index, with each axis parameterized over time. We assumed that a good pharmacodynamic index should present a clear and continuous relationship between the time course of its values and the time course of the bacterial killing as seen with the Zhi model. Preliminary work showed that some pharmacodynamic indices were very similar. A good sensitivity to the change in the values of the MIC was shown for AUC/MIC and also for T > MIC. In addition, the time courses of some other pharmacodynamic indices were very similar. Since AUC/MIC is easily calculated and shows more sensitivity, it appeared to be the best of the indices mentioned above for the concentration-dependent drug, because it incorporated and used the MIC the best. T > MIC appeared to be the best index for a concentration-independent drug. We also propose a new composite index, weighted AUC (WAUC), which appears to be useful for both concentration-dependent and concentration-independent drugs.

[Individual variability of pharmacokinetic parameters of amikacin in the elderly: retrospective studies]

In previous works, we have shown: i) good parameter predictive performances of the USC*PACK Clinical Programs for amikacin therapy in the elderly, ii) no significant difference generally detected between estimated parameter values at days 7 and 14 after the beginning of therapy, iii) assurance of neither accumulation nor toxicity during therapy up to 14 days or more, in our conditions. The objectives of this study were to explore which elements best explained differences found in the pharmacokinetic parameters (PK) of the elderly patients, who had received several courses of amikacin therapy.

METHODS

patients' pharmacokinetic data and their medical records were retrospectively analyzed. Only patients who received amikacin therapy with at least a 2-month washout between their courses were studied. Two parameterizations of the 1-compartment PK model were used: one without covariates: Kel-Vol, where Kel = elimination rate constant and Vol = distribution volume, and another including covariates: Ks-Vs, with: Kel = Ks. CCr + Ki, where: Ks = renal fraction of Kel, Ki - non renal elimination, CCr = estimated creatinine clearance, and Vs = Vol/W, where Vs = distribution volume per kg and W = weight.

RESULTS

14 patients, 3 men and 11 women, fulfilled the criteria (4 of them satisfied the condition with 3 courses). They were 66 to 89 years old, their mean weight was 53.86 +/- 11.03 kg (46-71.5), their CCr averaged: 55.45 +/- 17.16 mL/min (14.84-96.27).

CONCLUSION

Among patients exhibiting changes (67%) in PK parameters between different courses of therapy, 42% could have the variability related to covariate (W, CCr) changes; in the others 58% the residual variability could be explained by different factors: severity of infection, immune system deficiency and/or particularly parenteral nutrition. Based on these result, we suggest including septic choc and parenteral nutrition as covariates during amikacin adaptive control.

[Adaptive control of therapeutics using amikacin in very old patients: retrospective analysis of efficacy and toxicity]

The authors previously showed the precision of adaptive control of amikacin therapy in elderly patients. The present retrospective study evaluated the effects of such therapy on outcomes. 48 patients, aged 80 +/- 5 years, with estimated creatinine clearance (eCCR) of 48 +/- 15 ml/mn, received amikacin initial dosage of 13.3 +/- 3.5 mg/kg/d, alone or with other drugs. Efficacy outcomes were: E1 = changes in dosage during therapy; E2 = fever reduction within 3 days after therapy; E3 = eradication of infection by culture data; E4 = reduction of white blood cell count (WCB) to normal; E5 = overall recovery. Toxicity outcomes were: T1 = subjective ototoxicity; T2 = nephrotoxicity, variation of serum creatinine low (between 18 et 44 mumol/l) or high (over 0.5 mg/dl).

RESULTS

E1: final dose = 11.8 +/- 5.1 mg/kg/d (NS), 57% reduced, 33% increased, during 15.1 +/- 9.3 days in therapy, with 88% having effective peaks over 15 micrograms/ml. E2: fever reduced within 3 days 16/37; after 12/37; no change, 9/37. E3: cultures became negative, 13/28. E4: WBC fell early, 10/21; late, 7/21; no change, 2/21. E5: recovery 36; death, 8; change in therapy, 3. T1: no clinical signs of ototoxicity. T2: low(+), 9/51; low(-), 11/51; high(-), 7/51. final eCCR: 48 +/- 14 ml/mn (NS); no nephrotoxicity. These results suggest that adaptive control of amikacin regimens yields good efficacy and avoid toxicity in the Elderly. However, prospective controlled clinical trials should be done for confirmation.